Bacterial ecology on burn wound and antibacterial agent therapy / 中华烧伤杂志

The main factors influencing the bacterial ecology on burn wound are the selection of antibacterial agents and systemic antibiotic. Some antibacterial agents more active against P. aeruginosa were developed in 1960s, and the detection rate of P. aeruginosa on burn wound has been declined, and the detection rate of Enterobacteriaceae species and Acinetobacter SPP. has been raised since then. In 1990s, the third generation Cephalosporin was widely used in burn unit and the detection rate of staphylococcus aureus showed an increased trend. Especially, the positive rate of MRSA was increased significantly. Under the selection pressure of antibacterial agent, the resistant strains are rapidly increased and the antibiotics against opportunistic pathogen on burn wound should be selected continuously. Finally, the bacterial ecology pattern on burn wound is changing incessantly. The result is that the prevalence of infection of multi-drug resistance strains and opportunistic pathogen appears on burn wound. In order to optimize the antibiotic therapy, the bacterial ecology pattern on burn wound has to be investigated, and the dominant pathogen including invasive and currently prevailing strains in the burn unit also should always be surveyed. In addition, we also should know the mechanisms of bacterial resistance. The regular surveillance of antibiotic resistance in the clinical isolates is the most important and valuable for understanding the trend of bacterial resistance. The antibiotic therapy should be decided according to the result of susceptibility tests.

An understanding of burn infection / 中华烧伤杂志

Burn infection occurs when pathogenic bacteria colonized on the burn wound surface, and they then invaded the viable tissue causing sepsis or sepsis with blood stream invasion. This infection pattern is particular to burn injury. Both in a model of pseudomonas burn wound sepsis and a clinical study of early eschar excision for bacteria quantification indicate that the bacteria not only are located on the burn wound surface but also invaded the deeper tissues. Finally, the bacteria penetrate into the neighboring viable tissue and even blood vessels. Therefore, we can say that burn infection is from local wound infection to invasive infection, and finally sepsis is developed ,and it is termed as burn wound sepsis. The cutoff count of subeschar tissue bacteria is 10(5)/g. However, the burn wound sepsis may not occur when the number of subeschar tissue bacteria reaches 10(5)/g. The criteria for the diagnosis of burn wound sepsis are mainly listed as below: (1) The number of bacteria in the subeschar reaches > or =10(5)/g. (2) Bacteria can be detected in the biopsy specimen. (3) Sepsis associated symptoms and signs. However, the sepsis associated symptoms and signs must be obvious in patients to make the clinical diagnosis of burn wound sepsis. If the sepsis associated symptoms and signs do not appear, we should not make the diagnosis of burn wound sepsis eyen with the number of bacteria in the subeschar tissue reaching 10(5)/g or bacteria can be found in the biopsy specimen. Sepsis has been defined as the body % response to bacteria and their products. The occurrence of sepsis depends primarily on immune function and stress response intensity, and it is closely related to wound infection degree such as bacteria density and invasion depth in the burn wound, or plasma endotoxin level to certain extent.

Protective effect of lytic cocktail (inhibition of stress) on lung injury in severe burn rat / 中华烧伤杂志

<p><b>OBJECTIVE</b>To investigate the protective effect of inhibition of stress (lytic cocktail) on lung injury in severe burn rats at early stage.</p><p><b>METHODS</b>Sprague-Dawley rats inflicted with 30% TBSA full-thickness burn were randomly divided into A group (n = 36, fluid resuscitation with administration of lytic cocktail), B group (n = 36, fluid resuscitation only). Lung function was evaluated by partial pressure of oxygen (PaO2) in arterial blood and histopathologic changes on 3, 5, 7, 10 post burn day (PBD). The levels of malonyldialdehyde (MDA), myeloperoxidase (MPO), tumor necrosis factor-alpha(TNF-alpha) and interferon-gamma (IFN-gamma) in lung tissue were measured at the same time points.</p><p><b>RESULTS</b>The PaO2 level in A group on 3 PBD (12.58 +/- 0.41 kPa) was significantly higher than that in B group (8.86 +/- 0.23 kPa, P < 0.01). Compared with those in B group, the levels of MDA and MPO were significantly decreased in A group at each time point (P < 0.05 or 0.01), the levels of TNF-alpha on 3, 5, 7 PBD (P < 0.05 or 0.01) and IFN-gamma on 5, 7, 14 PBD (P < 0.01) were also decreased in A group. Swollen lung mesenchyme was alleviated, infiltration of inflammatory cell was lessened in A group.</p><p><b>CONCLUSION</b>Lytic cocktail combined with immediate fluid resuscitation can inhibit stess response, downregulate the expression of inflammatory factor, ameliorate lung function in severe burn rat at early stage.</p>

The antagonistic effect of recombinant human decorin on TGF-beta1 stimulation of fibroblasts in collagen lattices / 中华烧伤杂志

<p><b>OBJECTIVE</b>To mimic contact pattern between decorin and TGF-beta1, in vivo, and investigate the antagonistic effect of recombinant human decorin on TGF-beta1 stimulation of hypertrophic scar fibroblasts in collagen lattices.</p><p><b>METHODS</b>Fibroblasts populated collagen lattices (FPCL) model was adopted in the study, and they were divided into control group, decorin group [2mg/L recombinant human decorin (rh-decorin) was administered to FPCL], TGF-beta1 group (5 microg/LTGF-beta1 was administered to the culture medium), and TGF-beta1 + decorin group (2mg/L rh-decorin was administered to FPCL, then culture medium containing 5 microg/L TGF-beta1 was added into FPCL). Changes in PAI-1 and alpha-SMA protein expression in scar fibroblasts in collagen lattices were detected with Western blotting at 12 post-administration hour (PAH), 24 PAH, 48 PAH, and 72 PAH, and expressions of PAI-1 and alpha-SMA mRNA were concomitantly examined by RT-PCR.</p><p><b>RESULTS</b>The contraction of FPCL at each time-point in control group was obviously attenuated compared with that in decorin group, but it was significantly intensified compared with that in TGF-beta1 group. The expression of PAI-1 and alpha-SMA mRNA and protein in TGF-beta1 group (3482 +/- 211, 4320 +/- 272, 0.89 +/- 0.15, 0.56 +/- 0. 11) were markedly increased than those in control group (1764 +/- 147, 1699 +/- 146, 0.29 +/- 0.06, 0.21 +/- 0.06, P < 0.01), while no obvious difference of them was found between control and other two groups.</p><p><b>CONCLUSION</b>Stimulation of scar fibroblasts by TGF-beta1, can be suppressed when rh-decorin is blended into collagen lattices, indicating that decorin is effective in neutralizing TGF-beta1 in vitro. The pathogenesis of hypertrophic scar might be related to up-regulation of TGF-beta1 with the lack of decorin after cutaneous injury.</p>

The influence of topical application of insulin on the formation of basement membrane in scalded rats / 中华烧伤杂志

<p><b>OBJECTIVE</b>To investigate the influence of topical application of insulin on the formation of basement membrane (BM) in rats with deep partial thickness scald.</p><p><b>METHODS</b>Ninety-six SD rats were inflicted with deep partial thickness scald on the back and were randomized into A group (n = 48, with subcutaneous injection of 2 ml of isotonic saline on the 1 post scald day (PSD)) and B group (n = 48, with subcutaneous injection of 0.1 U of insulin and 2 ml of isotonic saline on the 1 PSD). The rats received the treatment every other day until wound re-epithelization completed. Then the rats were sacrificed on 2, 3, 4, 5, 6, 10, 14 PSD, and on the day when the wound re-epithelialized completely. The skin samples of 1 cm in width were harvested at the edge of the wound for reticular fiber staining and for morphological observation of the wound BM with transmission electron microscope. The expression of laminin-5 mRNA and laminin in keratinocyte was determined by RT-PCR and Western blotting, respectively.</p><p><b>RESULTS</b>Integrated and continuous structure of the basement membrane was observed in B group. Laminin-5 mRNA expression was much higher in B group than that in A group on 10 and 14 PSD (P < 0.05 or P < 0.01). Laminin-5 mRNA expression was decreased in both groups when epithelialization completed. But the Laminin-5 protein expression on 14 PSD and the day of epithelization (56 +/- 8, 101 +/- 13) was obviously higher in B group than that in A group (39 +/- 5, 73 +/- 16), (P < 0.05).</p><p><b>CONCLUSION</b>Subcutaneous injection of 0.1 U insulin beneath the scald wound is beneficial to the acceleration of the wound re-epithelialization process, and to the improvement of the wound healing quality.</p>

Influence of stress inhibition on invasive infection in burn wound during early postburn stage in severely burned rats / 中华烧伤杂志

<p><b>OBJECTIVE</b>To investigate the influence of inhibition of stress on the survival rate, organ dysfunction and (Th)1/Th2 cytokine profiles of the rats with invasive infection in the wound at early postburn stage.</p><p><b>METHODS</b>Sprague-Dawley rats inflicted with 30% TBSA full thickness burn were randomly divided into A (n = 36, with immediate resuscitation), B (n = 36, with immediate resuscitation and lytic cocktail administration). After subeschar injection of 0.1 ml Pseudomonas aeruginosa (10(8) CFU/ml) on 3rd postburn day, the subeschar bacterial quantitative analysis, the survival rate at 96 hours after bacteria injection, the parameters of organ dysfunction and the mRNA expression of IL-2, IL-4, IL-10 and IFN-gamma were determined by corresponding methods.</p><p><b>RESULTS</b>The quantity of subeschar bacteria was larger than 1 x 10(5)/gram in both groups. The survival rate in B group (66.7 +/- 2.6)% was obviously higher than that in A group (33.3 +/- 1.7)%, (P < 0.01). Inflammatory infiltration and pathological changes in the internal organs in B group were alleviated obviously compared with A group. The expression of IL-2 mRNA in B group was significantly lower than that in A group before bacterial inoculation, but increased at 48 and 96 hours after bacterial inoculation, while it was lowered in A group at the same time points (P < 0.05). The expression of IFN-gamma mRNA in A group was significantly lower than that in B group (P < 0.01), while that of IL-4 and IL-10 mRNA in A group was evidently higher than that in B group (P < 0.05 approximately 0.01).</p><p><b>CONCLUSION</b>Inhibition of the stress response during early postburn stage could be beneficial to the prevention of the bacterial invasion due to the changes in Th1/Th2 ratio.</p>

Expression of keratinocyte basement membrane related genes during the process of re-epithelialization of burn wound in scalded rats / 中华烧伤杂志

<p><b>OBJECTIVE</b>To study the expression of keratinocyte (KC) basement membrane (BM) related genes during the process of re-epithelialization of burn wound in scalded rats with cDNA microarray technique.</p><p><b>METHODS</b>Twenty-four SD rats were inflicted with deep partial thickness scald with an area of 45 cm(2) on the back, and they were randomly divided into A [3 postscald day (PSD)], B (10 PSD), C (14 PSD) and D (re-epithelialization complete day) groups, with 6 rats in each group. Tissue samples were harvested from 1 cm of wound margin on 3, 10 and 14 PSD. On the re-epithelialization complete day, tissue samples were harvested from the center of the wound in D group and digested with enzyme into KC suspensions. Skin samples from the back of 6 uninjured rats were taken as normal control. The differential expression of KC BM related genes during different stages of re-epithelialization was assayed with cDNA microarray.</p><p><b>RESULTS</b>The expression of laminin (LN) gamma 1 (2.068) and integrin beta8 (2.200) was up-regulated on 3 PSD compared with that in control. The expression of integrin beta1 and LN receptor 1 was up-regulated on 10 and 14 PSD, (2.472 and 2.658), while that of integrin beta2 and beta1 (0.419 and 0.462) down-regulated on 10 and 14 PSD, and the expression of type IV collagen alpha1 and alpha3 was up-regulated during re-epithelialization.</p><p><b>CONCLUSION</b>The expression of integrin beta1, LN gamma 1, LN receptor 1, type IV collagen alpha1 and alpha3 genes were up-regulated during re-epithelialization, which might be beneficial to the construction of BM in new skin and the formation of stable conjunction between KC and BM.</p>

The content of decorin and its mRNA expression in normal human skin and hyperplastic scars / 中华烧伤杂志

<p><b>OBJECTIVE</b>To investigate the content of decorin and its mRNA expression in normal human skin and hyperplastic scars at different stages, so as to explore the relationship between the change of decorin and its synthesis.</p><p><b>METHODS</b>Scar tissue samples from 22 patients undergoing scar excision and 10 specimens of normal skin or prepuce were obtained. The content and distribution of decorin in the tissue samples were determined with immunohistochemistry and Western blot, and the expression of decorin mRNA was detected by in situ hybridization.</p><p><b>RESULTS</b>The content of decorin was rich in the normal skin dermis with lower expression of the mRNA. In contrast, the decorin content was scarce in hyperplastic scars (HS) within 6 months, but increased gradually beginning from 7 to 12 months, and increased continuously for 13 to 36 months. There was no difference between the decorin content in normal skin and that in HS after 36 months (P > 0.05). Furthermore, the mRNA expression level in HS tissue was lower than that in normal skin within 6 months, but increased from 7 to 12 months. The mRNA expression continuously increased during 13 to 36 months and then returned to the level similar to that in normal skin thereafter.</p><p><b>CONCLUSION</b>The decrease of decorin in hyperplastic scar was resulted primarily from reduced synthesis. The increase in decorin level coincided with the time of scar tissue stabilization, which implied that the delayed appearance was correlated with the formation of HS.</p>

Effects of topical application of insulin on the wound healing in scalded rats / 中华烧伤杂志

<p><b>OBJECTIVE</b>To investigate the effects of topical application of small dose of insulin on the wound healing of the scalded rats, so as to explore its mechanism.</p><p><b>METHODS</b>The rats employed in the study were subjected to deep partial thickness burn and were divided into group A (with subcutaneous injection of isotonic saline into the rat wounds as control), B and C (with subcutaneous injection of 0.1 U and 1 U insulin in the rat wounds respectively) and D (with subcutaneous injection of 0.1 U insulin in the rat abdomen as control). The wound healing time and wound healing rate were assessed every other day after 3 postburn days (PBDs). The histological changes of the wounds after injection were examined, the changes in the cell cycle of epidermal cells in the wound were analyzed by flow-cytometry, and blood glucose concentration of each group was determined.</p><p><b>RESULTS</b>The wound healing time in group B (18.36 +/- 4.12 d) was significantly shorter than that in other groups (A: 24.57 +/- 5.19 d, C: 21.46 +/- 2.97 d, D: 24.50 +/- 1.05 d, P < 0.01). The wound healing rate of the rats in group B in 5, 9, 11, 13, 15, 17 and 19 PBD was obviously higher than that in group A, and was markedly higher than that in group C on 17 PBD (P < 0.05 - 0.01). The epithelial layer was thinner with less epidermal nails but much more fibroblasts in epidermal layer in group A, while the epithelial layer was thicker with abundant epidermal nails in group B and C with many fibroblasts in the dermis. The amount of cells in S phase at 4 PBD in group B was dramatically higher than that in group A, and cells in G2M phase at 4 - 5 PBD in group B was also higher than that in group A and C (P < 0.05 - 0.01). The blood level of glucose in group A and B fluctuated between 3.42 to 4.62 mmol/L at 24 PBH, while that in group C and D decreased obviously 1 hour after injection (P < 0.01), but gradually returned to normal 4 hours after injection.</p><p><b>CONCLUSION</b>Local injection of small dose of insulin may accelerate burn wound healing due to its role in promoting the proliferation and division of the repairing cells.</p>